Multi-stage sequential telescopic hydraulic cylinder capable of converting thrust step by step

Abstract

The embodiment of the invention discloses a multistage sequential telescopic hydraulic cylinder capable of converting thrust step by step, which belongs to the technical field of hydraulic cylinders and comprises a hydraulic cylinder body. The multiple piston assemblies are coaxially and sequentially arranged in the hydraulic cylinder body in a nested mode, oil holes are coaxially formed in the bottoms of the piston assemblies, the multiple oil holes form an oil cavity, and an oil inlet cavity is formed in the innermost piston assembly. The bottom of each piston assembly is provided with an extending starting groove communicated with the oil cavity. A connecting accessory is arranged at the top of the piston assembly, and a first cavity oil port and a second cavity oil port which are communicated with the oil inlet cavity are formed in the connecting accessory. A core tube is arranged in the oil inlet cavity, one end of the core tube is communicated with the first cavity oil port, and the other end of the core tube is communicated with the oil hole of the innermost piston assembly. The arrangement mode that the multiple piston assemblies are coaxially and sequentially nested is adopted, and hydraulic oil is guided in through the core pipe and the oil holes and acts on the piston assemblies at all stages. And sequential extension is realized by utilizing the characteristic that the output force of the hydraulic cylinder is in direct proportion to the effective area of the piston.

Description

Technical Field

[0001] The present application relates to the technical field of hydraulic cylinders, and in particular to a multi-stage sequential telescopic hydraulic cylinder capable of changing thrust step by step. Background Art

[0002] As a key actuator in hydraulic systems, hydraulic cylinders have been widely used in the field of engineering machinery due to their flexible movements and ability to effectively transmit forces. Traditional single-piston-rod hydraulic cylinders are mainly designed to withstand vertical forces. In applications that require long strokes, the length of the entire hydraulic cylinder needs to be increased accordingly, which not only limits its flexibility, but also makes single-acting cylinders even more incapable of meeting the requirements, especially in situations where variable thrust is required.

[0003] Although ordinary multi-stage hydraulic cylinders have solved the problem of long stroke to a certain extent, their number of stages is usually limited to less than three, and the thrust output is limited to the annular action area, which is difficult to meet the demand for large thrust. In order to increase the thrust, it is often necessary to increase the cylinder diameter, but this will undoubtedly take up more space and increase the weight of the cylinder, thus limiting its application in many occasions.

[0004] Therefore, the common multi-stage cylinders widely used at present often have difficult to reconcile contradictions between thrust, space and weight. They either cannot meet the demand for large thrust, or occupy too much space and are too heavy. At the same time, since the oil circuit piston rod wall needs to be drilled, it is affected by the pressure difference and pressure loss, and the synchronization stability fluctuates greatly, and safety cannot be guaranteed. In addition, the thicker piston rod also increases the weight of the entire cylinder. Summary of the invention

[0005] The purpose of the present application is to provide a multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change, so as to solve the problem in the prior art that it is difficult to reconcile the thrust, space and weight of the multi-stage hydraulic cylinder.

[0006] In order to solve the above technical problems, this application is implemented by adopting the following technical solutions:

[0007] On the one hand, the multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change of the present invention includes a multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change, characterized in that it includes:

[0008] Hydraulic cylinder body;

[0009] A piston assembly is nested in the hydraulic cylinder body, the piston assembly comprises a plurality of piston assemblies nested in sequence, the bottoms of the plurality of piston assemblies are provided with coaxially arranged oil holes, the innermost piston assembly has an oil inlet cavity, the oil cavity formed by the plurality of oil holes, and the bottom of each piston assembly has a stretching start groove connected to the oil cavity;

[0010] A connecting accessory connected to the top of the innermost piston assembly, on which a first chamber oil port and a second chamber oil port communicating with the oil inlet chamber are provided;

[0011] The core tube is located in the oil inlet cavity, one end of which is connected to the first cavity oil port and the other end of which is connected to the oil hole of the innermost layer of the piston assembly.

[0012] During operation, the hydraulic oil first enters the core tube through the first chamber oil port, and then enters the oil chamber. At this time, the hydraulic oil acts on the bottom of each piston assembly through the extension start groove. The start groove prevents the bottom of each layer of piston assemblies from conflicting with each other, resulting in the inability of hydraulic oil to enter. Since the bottom area of ​​each piston assembly gradually increases from the inside to the outside, its contact area with the hydraulic oil is also different accordingly, so under the action of the oil pressure, each level of piston will produce different pressure responses. The outermost piston assembly will be pushed out first because it has the largest contact area and the greatest pressure. When a certain layer of piston assemblies moves to the end of its stroke under the action of the oil pressure, as the oil pressure continues to rise, the next layer of piston assemblies will begin to extend. The thrust generated by each layer of piston assemblies when extending is proportional to the contact area between its bottom surface and the hydraulic oil, thereby realizing the sequential extension of the piston assemblies layer by layer.

[0013] The present invention adopts a setting mode in which multiple piston assemblies are coaxial and nested in sequence, so that the structure of the entire hydraulic cylinder is more compact, the occupied space is smaller, and the weight is lighter while ensuring the thrust of the hydraulic cylinder. By realizing the sequential extension of the piston rod, the confusion and damage that may be caused by the simultaneous extension of multiple-stage pistons are avoided, and the stability and reliability of the equipment are improved.

[0014] Optionally, the piston assembly comprises: an axially arranged piston and a piston rod;

[0015] The piston rod is provided with an oil return port penetrating through its side wall. When the piston rod has not reached the maximum extension state, there is an annular compression oil chamber with an open top end between every two adjacent piston rods and between the piston rod located at the outermost layer and the hydraulic cylinder body. A guide sleeve is provided at the open end of each compression oil chamber. Each guide sleeve is connected to the piston rod located outside the compression oil chamber, and the guide sleeve located at the outermost layer is connected to the hydraulic cylinder body. When a certain piston rod reaches the maximum extension state, there is a retraction start groove connected to the oil return port on the piston rod between the piston connected to the piston rod and the guide sleeve that conflicts with the piston.

[0016] When the hydraulic cylinder needs to retract, the hydraulic oil enters the oil inlet chamber through the second chamber oil port, and enters the retraction start groove through the oil return port. Under the action of the hydraulic oil, the piston is separated from the guide sleeve, thereby forming an annular compression oil chamber. After the hydraulic oil enters the compression oil chamber, it moves the compression piston downward, thereby achieving the retraction of the piston assembly. When the inner layer piston assembly is fully retracted, the oil return port on the piston rod of the adjacent outer layer is connected to the compression oil chamber, and the above steps will be repeated until all the piston assemblies are fully retracted.

[0017] In the initial state when the hydraulic cylinder needs to retract, the piston assembly is in the extended state. When retraction is required, the hydraulic oil enters the oil inlet chamber through the second chamber oil port. Then it enters the retraction start groove through the oil return port. The start groove is designed to separate the piston and the guide sleeve under the action of the hydraulic oil, thereby forming an annular compression oil chamber. After the annular compression oil chamber is formed, the hydraulic oil will enter the compression oil chamber. The hydraulic pressure will push the piston to move toward the bottom of the hydraulic cylinder, that is, to move in the retraction direction.

[0018] When the innermost piston assembly is fully retracted, the oil return port of the adjacent outer piston assembly will be connected to the previously formed compression oil chamber. This connection process will repeat the above steps of hydraulic oil flow and piston assembly retraction, but this time for the next level of piston assembly. As the process continues, each layer of piston assembly will retract in turn until all piston assemblies are fully retracted into the hydraulic cylinder.

[0019] Optionally, the retraction start groove includes at least one of a first groove arranged at the end of the piston and a second groove arranged at the bottom of the guide sleeve.

[0020] First groove: set at the end of the piston. When the hydraulic oil enters the oil inlet chamber through the second chamber oil port, part of the hydraulic oil will flow into the gap between the piston and the guide sleeve through the first groove on the piston. This gap will gradually expand under the action of the hydraulic oil, and eventually the piston and the guide sleeve will be completely separated, thus forming an annular compression oil chamber.

[0021] Second groove: set at the bottom of the guide sleeve. Similar to the first groove, when the hydraulic oil flows into the second groove at the bottom of the guide sleeve, part of the hydraulic oil will flow into the gap between the piston and the guide sleeve through the second groove. This gap will gradually expand under the action of the hydraulic oil, and eventually the piston and the guide sleeve will be completely separated, thereby forming an annular compression oil chamber. This separation is also to form an annular compression oil chamber to further promote the retraction of the piston.

[0022] It should be noted that the retraction start groove does not necessarily include both the first groove and the second groove. According to specific requirements, it can be any one of the two or a combination of the two. When the combination of the two is used, they may work together in the separation process between the piston and the guide sleeve, thereby ensuring a smooth and reliable retraction process.

[0023] It should be noted that this embodiment does not limit the shape, size, and position of the first groove and the second groove, as long as the requirements are met.

[0024] Optionally, the flow rate of the second chamber oil port is the same as the total flow rate of all oil return ports on each of the piston rods.

[0025] In order to avoid the hydraulic oil in the compression oil chamber entering the next layer of compression oil chamber, the hydraulic oil pressure in the previous layer of compression oil chamber is reduced due to the oil inlet of the second chamber being less than the oil return port flow rate. The piston assembly rebounds and extends due to the loss of sufficient hydraulic pressure, thus affecting the normal operation of the hydraulic cylinder. In this solution, the oil flow rate of the second chamber is the same as the total flow rate of all the oil return ports on each of the piston rods. By accurately controlling the inflow and outflow of hydraulic oil, the piston assembly can be retracted smoothly and orderly.

[0026] Optionally, the cross-sectional area of ​​the compression oil chamber decreases from the inner layer to the outer layer.

[0027] In this solution, since the cross-sectional area of ​​the compression oil chamber decreases from the inner layer to the outer layer, when the hydraulic oil enters each layer of the compression oil chamber, the compression oil chamber located in the innermost layer exerts the greatest pressure on the piston. When the hydraulic oil enters the compression oil chamber of the next layer, it will not cause the piston of this layer to rebound due to the greater pressure of the outer layer piston of the adjacent hydraulic oil. The piston assembly can be retracted in sequence starting from the outermost layer. As the hydraulic oil continues to flow in, the compression oil chamber of the inner layer is gradually filled, and the corresponding pressure is generated to push the piston assembly to continue to retract. This solution not only ensures that the piston assembly can retract from the outermost layer in a predetermined order, but also reduces the risk of piston assembly jamming or damage due to uneven pressure, and increases the stability of the hydraulic cylinder.

[0028] Optionally, the axial area of ​​the extension start slot on each piston assembly decreases from the outside to the inside, thereby ensuring that the piston assembly can be started in sequence from the outside to the inside during the extension start process.

[0029] Optionally, each of the piston assemblies has a plurality of oil holes which are axially arranged and equidistantly distributed around the circumference, and the oil holes on different piston assemblies do not intersect in the axial direction.

[0030] Multiple axially arranged and equidistantly distributed oil holes allow the hydraulic oil at the bottom of the piston to contact the bottom of the adjacent inner layer piston more quickly. This promotes the uniform distribution and rapid flow of the hydraulic oil, thereby improving the response speed and efficiency of the extension of the piston assembly. This makes the extension and connection of each layer of the piston assembly smoother.

[0031] Optionally, each guide sleeve is connected to a piston rod located outside the compression oil chamber by a gland-type threaded connection, and the guide sleeve located at the outermost layer is connected to a hydraulic cylinder body by a gland-type threaded connection.

[0032] The inner gland threaded connection ensures that the guide sleeve can be firmly fixed on the piston rod and forms a good seal with the adjacent inner piston rod. The main function of the guide sleeve is to guide the piston assembly to move smoothly and linearly in the hydraulic cylinder to prevent it from being worn or damaged due to uneven force or deflection. The inner gland threaded connection can ensure that the connection between the guide sleeve and the piston rod is tight and reliable, and is not easy to loosen or leak.

[0033] Optionally, the connecting accessory is an earring, and the earring is threadedly connected to the top of the innermost piston assembly.

[0034] When the present invention is used, it needs to be installed and connected with an external host or other devices, equipment, and structural parts. The earring is a commonly used connecting part, which is usually connected to the top of the innermost piston assembly through a thread and can withstand a certain eccentric load or torque. The hinge point of the earring can be fixedly connected to the structural part by a joint bearing or a bushing. The use of a joint bearing or a bushing can ensure the flexibility and durability of the connection and reduce failures caused by loose connection or wear.

[0035] Compared with the prior art, the beneficial effects achieved by the present application are as follows: the present invention adopts a setting mode in which multiple piston assemblies are coaxial and nested in sequence, and hydraulic oil is introduced and acts on each level of piston assemblies through a core tube and an oil hole. The sequential start of each level of pistons is achieved by extending the start groove. The characteristic that the output force of the hydraulic cylinder is proportional to the effective area of ​​the piston is used to achieve sequential extension. During the retraction process, the flow direction of the hydraulic oil is controlled through the return oil hole and the compression oil chamber to achieve the retraction of the piston assembly. The sequential retraction of the piston assembly is achieved by controlling the oil inlet amount or the cross-sectional size of the compression oil chamber.

[0036] The invention makes the structure of the entire hydraulic cylinder more compact, occupies less space and is lighter in weight while ensuring the thrust of the hydraulic cylinder. The sequential extension and retraction of the piston rod is realized, and the confusion and damage that may be caused by the simultaneous extension of multiple-stage pistons are avoided, thereby improving the stability and reliability of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 is a cross-sectional view of some embodiments provided by the present application in a retracted state;

[0039] Figure 2 It is a schematic diagram of the retraction start groove structure of some embodiments provided in the present application.

[0040] Description of reference numerals:

[0041] 1-Hydraulic cylinder body; 2-Piston assembly; 3-Connecting accessories; 4-Core tube; 5-Compression oil chamber; 6-Guide sleeve; 7-Retraction start groove; 21-Oil hole; 22-Piston; 23-Piston rod; 24-Oil inlet chamber; 31-First chamber oil port; 32-Second chamber oil port; 71-First groove; 72-Second groove; 221-Extension start groove; 222-Oil hole; 231-Oil return port. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present disclosure / application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use.

[0043] Embodiment 1

[0044] This embodiment introduces a multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change. Figure 1The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change in this embodiment includes: a hydraulic cylinder body 1, including a cylinder bottom and a cylinder barrel. It provides a solid support for the entire hydraulic cylinder and a space for accommodating a piston assembly. The piston assembly is nested in the hydraulic cylinder body 1, including a plurality of piston assemblies 2 nested in sequence, and a coaxially arranged oil hole 21 is opened at the bottom of the plurality of piston assemblies 2. The plurality of oil holes 21 form an oil cavity, and an oil inlet cavity 24 is provided inside the innermost piston assembly 2 for receiving oil pressure from the outside. Each piston assembly 2 has a stretching start groove 221 connected to the oil cavity at the bottom. A connecting attachment 3 is connected to the top of the innermost piston assembly 2, and is provided with a first cavity oil port 31 and a second cavity oil port 32 connected to the oil inlet cavity 24. A core tube 4 is located in the oil inlet cavity 24, one end of which is connected to the first cavity oil port 31 and the other end of which is connected to the oil hole 21 of the innermost piston assembly 2.

[0045] During the extension process of the hydraulic cylinder of this embodiment, the hydraulic oil first enters the core tube 4 through the first chamber oil port 31, and then enters the oil chamber. At this time, the hydraulic oil acts on the bottom of each piston assembly 2 through the extension start groove 221. The start groove prevents the bottom of each layer of piston assemblies 2 from conflicting with each other, resulting in the inability of hydraulic oil to enter. Since the bottom area of ​​each piston assembly 2 gradually increases from the inside to the outside, its contact area with the hydraulic oil is also different accordingly, so that under the action of the oil pressure, each level of piston assembly will produce different pressure responses. The outermost piston assembly 2 will be pushed out first because it has the largest contact area and the greatest pressure. When a certain layer of piston assembly 2 moves to the end of its stroke under the action of the oil pressure, as the oil pressure continues to rise, the next layer of piston assembly 2 will begin to extend. The thrust generated by each layer of piston assembly 2 when extending is proportional to the contact area between its bottom surface and the hydraulic oil, thereby realizing the sequential extension of the piston assembly 2 layer by layer.

[0046] The present invention adopts a coaxial and sequentially nested arrangement of multiple piston assemblies 2, which makes the structure of the entire hydraulic cylinder more compact, occupies less space and is lighter in weight while ensuring the thrust of the hydraulic cylinder. By realizing the sequential extension of the piston rod 23, the confusion and damage that may be caused by the simultaneous extension of multiple-stage pistons are avoided, thereby improving the stability and reliability of the equipment.

[0047] In this embodiment, the piston assembly 2 includes an axially arranged piston 22 and a piston rod 23. The piston rod 23 has an oil return port 231 penetrating its side wall. When the piston rod 23 has not reached the maximum extension state, there is a compression oil chamber 5 with an open top end between every two adjacent piston rods 23 and between the outermost piston rod 23 and the hydraulic cylinder body 1. A guide sleeve 6 is provided at the open end of each compression oil chamber 5. Each guide sleeve 6 is connected to the piston rod 23 located outside the compression oil chamber 5, and the outermost guide sleeve 6 is connected to the hydraulic cylinder body 1. When a certain piston rod 23 reaches the maximum extension state, there is a retraction start groove 7 connected to the oil return port 231 on the piston rod 23 between the piston 22 connected to the piston rod 23 and the guide sleeve 6 that conflicts with the piston 22.

[0048] During the retraction process of the hydraulic cylinder of this embodiment, the hydraulic oil enters the oil inlet chamber 24 through the second chamber oil port 32, and enters the retraction start groove 7 through the oil return port 231. Under the action of the hydraulic oil, the piston 22 is separated from the guide sleeve 6, thereby forming an annular compression oil chamber 5. After the hydraulic oil enters the compression oil chamber 5, it moves the compression piston 22 downward, thereby achieving the retraction of the piston assembly 2. When the inner layer piston assembly 2 is fully retracted, the oil return port 231 on the piston rod 23 of the adjacent outer layer is connected to the compression oil chamber 5, and the above steps will be repeated until all the piston assemblies 2 are fully retracted.

[0049] In the initial state when the hydraulic cylinder needs to be retracted, the piston assembly 2 is in an extended state. When retraction is required, the hydraulic oil enters the oil inlet chamber 24 through the second chamber oil port 32. Then it enters the retraction start groove 7 through the oil return port 231. The start groove is designed to separate the piston and the guide sleeve 6 under the action of the hydraulic oil, thereby forming an annular compression oil chamber 5. After the annular compression oil chamber 5 is formed, the hydraulic oil will enter the compression oil chamber 5. The hydraulic pressure will push the piston to move toward the bottom of the hydraulic cylinder, that is, to move in the retraction direction.

[0050] When the innermost piston assembly 2 is fully retracted, the oil return port 231 of the adjacent outer piston assembly 2 will be connected to the previously formed compression oil chamber 5. This connection process will repeat the above-mentioned steps of hydraulic oil flow and piston assembly 2 retraction, but this time for the next layer of piston assembly 2. As the process continues, each layer of piston assembly 2 will be retracted in turn until all piston assemblies 2 are fully retracted into the hydraulic cylinder.

[0051] Furthermore, in the present embodiment, the cross-sectional area of ​​the compression oil chamber 5 decreases from the inner layer to the outer layer. Since the cross-sectional area of ​​the compression oil chamber 5 decreases from the inner layer to the outer layer, when the hydraulic oil enters each layer of the compression oil chamber 5, the compression oil chamber 5 located in the innermost layer exerts the greatest pressure on the piston 22. When the hydraulic oil enters the compression oil chamber 5 of the next layer, it will not cause the piston of this layer to rebound due to the greater pressure of the outer layer piston 22 of the adjacent hydraulic oil. The piston assembly 2 can be retracted in sequence starting from the outermost layer. As the hydraulic oil continues to flow in, the compression oil chamber 5 of the inner layer is gradually filled, and the corresponding pressure is generated to push the piston assembly 2 to continue to retract. This solution not only ensures that the piston assembly 2 can retract from the outermost layer in a predetermined order, but also reduces the risk of the piston assembly 2 being stuck or damaged due to uneven pressure, and increases the stability of the hydraulic cylinder.

[0052] Embodiment 2:

[0053] Based on the same inventive concept as in Example 1, refer to Figure 1 The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change in this embodiment includes: a hydraulic cylinder body 1, including a cylinder bottom and a cylinder barrel. It provides a solid support for the entire hydraulic cylinder and a space for accommodating the piston assembly body. And includes five coaxial and sequentially nested piston assemblies 2 arranged in the hydraulic cylinder body 1. Each piston assembly 2 includes an axially arranged piston 22 and a piston rod 23, and the bottom of the five piston assemblies 2 are provided with coaxially arranged oil holes 21, and multiple oil holes 21 form an oil cavity. The innermost piston assembly 2 has an oil inlet cavity 24 for receiving oil pressure from the outside. The bottom of each piston assembly 2 has an extension start groove 221 connected to the oil cavity. Furthermore, the axial area of ​​the extension start groove 221 on each piston assembly 2 decreases from the outside to the inside. Thereby ensuring that the piston assembly 2 can be started in sequence from the outside to the inside during the extension start process.

[0054] In this embodiment, an earring is threadedly connected to the top of the innermost piston assembly 2. The earring is a commonly used connector, which is installed and connected to the external host or other devices, equipment, and structural parts through the earring, and can withstand a certain eccentric load or torque. The hinge of the earring can be fixedly connected to the structural part by a spherical bearing or a bushing. The use of spherical bearings or bushings can ensure the flexibility and durability of the connection and reduce failures caused by loose connections or wear. In addition to the earring end connection, the bottom of the hydraulic cylinder can also be connected to other structural parts. This connection method is usually used in scenarios where the position of the hydraulic cylinder needs to be fixed. In addition, a flange can be welded on the cylinder barrel and connected to other structural parts through the flange. This connection method is more secure and suitable for scenarios that need to withstand large loads or vibrations.

[0055] Furthermore, the earring is provided with a first cavity oil port 31 and a second cavity oil port 32 connected to the oil inlet cavity 24. A core tube 4 is provided in the oil inlet cavity 24. One end of the core tube 4 is connected to the first cavity oil port 31, and the other end is connected to the oil hole 21 of the innermost piston assembly 2.

[0056] To enable the hydraulic oil at the bottom of the piston 22 to contact the bottom of the adjacent inner piston 22 more quickly. In this embodiment, each piston assembly 2 has a plurality of oil holes 222 that are axially arranged and equidistantly distributed around the circumference, and the oil holes 222 located on different piston assemblies 2 do not intersect axially. The oil holes 222 promote the uniform distribution and rapid flow of the hydraulic oil, thereby improving the response speed and efficiency of the extension of the piston assembly 2. The extension connection of each layer of the piston assembly 2 is made smoother. Secondly, the oil holes 222 can also stabilize the piston assembly 2 to a certain extent. When the piston assembly 2 is in an extended or retracted state, the hydraulic oil will generate pressure on the side wall of the oil hole 222, thereby helping the piston assembly 2 to maintain a stable position in the hydraulic cylinder.

[0057] During the extension process of the hydraulic cylinder in this embodiment, the hydraulic oil first enters the core tube 4 through the first chamber oil port 31, and then enters the oil chamber. At this time, the hydraulic oil acts on the bottom of each piston assembly 2 through the extension start groove 221. The start groove avoids the bottom of each layer of piston assemblies 2 from conflicting with each other, resulting in the inability of hydraulic oil to enter. The axial area of ​​the start groove is different. It also ensures that the piston assemblies 2 can be started sequentially from the outside to the inside during the extension start process. Since the bottom area of ​​each piston assembly 2 gradually increases from the inside to the outside, the piston assemblies 2 are extended sequentially layer by layer. When a certain layer of piston assemblies 2 moves to the end of its stroke under the action of oil pressure, the hydraulic oil contacts the next layer of piston assemblies 2 through the extension start groove 221 and the oil hole 222, generating pressure to make the extension transition smoother.

[0058] The piston rod 23 of this embodiment has an oil return port 231 penetrating its side wall. When the piston rod 23 has not reached the maximum elongation state, there is a compression oil chamber 5 with an open top end between every two adjacent piston rods 23 and between the outermost piston rod 23 and the hydraulic cylinder body 1. A guide sleeve 6 is provided at the open end of each compression oil chamber 5. Each guide sleeve 6 is connected to the piston rod 23 located outside the compression oil chamber 5, and the guide sleeve 6 located at the outermost layer is connected to the hydraulic cylinder body 1. In this embodiment, the guide sleeve 6 is connected to the piston rod 23 located outside the compression oil chamber 5 by a gland-type thread, and the guide sleeve 6 located at the outermost layer is connected to the hydraulic cylinder body 1 by a gland-type thread. The gland-type thread connection ensures that the guide sleeve 6 can be firmly fixed on the piston rod 23 and form a good seal with the adjacent inner piston rod 23. The main function of the guide sleeve 6 is to guide the piston assembly 2 to move smoothly and linearly in the hydraulic cylinder to prevent it from being worn or damaged due to uneven force or deflection. The inner gland type threaded connection can ensure that the connection between the guide sleeve 6 and the piston rod 23 is tight and reliable, and is not easy to loosen or leak. Furthermore, when a piston rod 23 reaches the maximum extension state, a retraction start groove 7 connected to the oil return port 231 on the piston rod 23 is provided between the piston connected to the piston rod 23 and the guide sleeve 6 that contacts the piston.

[0059] refer to Figure 2 As shown, Figure 2 Only for Figure 1 The structure of the auxiliary explanation, the retraction start groove 7 includes a first groove 71 arranged at the end of the piston and a second groove 72 arranged at the bottom of the guide sleeve 6. When the hydraulic oil enters the oil inlet chamber 24 through the second chamber oil port 32, part of the hydraulic oil will flow into the gap between the piston and the guide sleeve 6 through the first groove 71 on the piston. This gap will gradually expand under the action of the hydraulic oil, and eventually the piston and the guide sleeve 6 will be completely separated, thereby forming an annular compression oil chamber 5. Similar to the first groove 71, when the hydraulic oil flows into the second groove 72 at the bottom of the guide sleeve 6, part of the hydraulic oil will flow into the gap between the piston and the guide sleeve 6 through the second groove 72. This gap will gradually expand under the action of the hydraulic oil, and eventually the piston and the guide sleeve 6 will be completely separated, thereby forming an annular compression oil chamber 5. This separation is also to form an annular compression oil chamber 5, so as to further promote the retraction of the piston. It should be noted that the retraction start groove 7 does not necessarily have to include the first groove 71 and the second groove 72 at the same time. According to specific needs, it can be any one of the two, or a combination of the two. In this embodiment, a combination of the two is used, and under the joint action, the piston and the guide sleeve 6 are separated to ensure a smooth and reliable retraction process.

[0060] During the retraction process of the hydraulic cylinder of this embodiment, the hydraulic oil enters the oil inlet chamber 24 through the second chamber oil port 32, and enters the retraction start groove 7 through the oil return port 231. Under the action of the hydraulic oil, the piston is separated from the guide sleeve 6, thereby forming an annular compression oil chamber 5. After the hydraulic oil enters the compression oil chamber 5, it moves the compression piston 22 downward, thereby achieving the retraction of the piston assembly 2. When the inner layer piston assembly 2 is fully retracted, the oil return port 231 on the piston rod 23 of the adjacent outer layer is connected to the compression oil chamber 5, and the above steps are repeated until all the piston assemblies 2 are fully retracted.

[0061] In the initial state when the hydraulic cylinder needs to be retracted, the piston assembly 2 is in an extended state. When retraction is required, the hydraulic oil enters the oil inlet chamber 24 through the second chamber oil port 32. Then it enters the retraction start groove 7 through the oil return port 231. The start groove is designed to separate the piston and the guide sleeve 6 under the action of the hydraulic oil, thereby forming an annular compression oil chamber 5. After the annular compression oil chamber 5 is formed, the hydraulic oil will enter the compression oil chamber 5. The hydraulic pressure will push the piston to move toward the bottom of the hydraulic cylinder, that is, to move in the retraction direction.

[0062] When the innermost piston assembly 2 is fully retracted, the oil return port 231 of the adjacent outer piston assembly 2 will be connected to the previously formed compression oil chamber 5. This connection process will repeat the above-mentioned steps of hydraulic oil flow and piston assembly 2 retraction, but this time for the next layer of piston assembly 2. As the process continues, each layer of piston assembly 2 will be retracted in turn until all piston assemblies 2 are fully retracted into the hydraulic cylinder.

[0063] In order to prevent the hydraulic oil in the compression oil chamber 5 from entering the next layer of compression oil chamber 5, the hydraulic oil pressure in the previous layer of compression oil chamber 5 is reduced due to the oil inlet amount of the second chamber oil port 32 being less than the flow rate of the return oil port 231. The piston assembly 2 rebounds and extends due to the loss of sufficient hydraulic pressure, thereby affecting the normal operation of the hydraulic cylinder. In this solution, the flow rate of the second chamber oil port 32 is the same as the total flow rate of all the return oil ports 231 on each of the piston rods 23. By accurately controlling the flow rate of hydraulic oil in and out, the piston assembly 2 can be retracted smoothly and orderly.

[0064] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present disclosure / application, and these improvements and modifications should also be regarded as the scope of protection of the present disclosure / application.

Claims

1. A multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change, characterized in that: include: Hydraulic cylinder body (1); A piston assembly is nested in the hydraulic cylinder body (1), the piston assembly comprising a plurality of piston assemblies (2) nested in sequence, the bottoms of the plurality of piston assemblies (2) are provided with coaxially arranged oil holes (21), the innermost piston assembly (2) has an oil inlet chamber (24), the plurality of oil holes (21) form an oil chamber, and the bottom of each piston assembly (2) has a stretching start groove (221) connected to the oil chamber; A connecting accessory (3) connected to the top of the innermost piston assembly (2), the connecting accessory (3) being provided with a first chamber oil port (31) and a second chamber oil port (32) which are connected to the oil inlet chamber (24); The core tube (4) is located in the oil inlet chamber (24), one end of the core tube (4) is connected to the first chamber oil port (31), and the other end of the core tube (4) is connected to the oil hole (21) of the innermost piston assembly (2).

2. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1 is characterized in that: The piston assembly (2) comprises: an axially arranged piston (22) and a piston rod (23); The piston rod (23) has an oil return port (231) penetrating its side wall. When the piston rod (23) has not reached the maximum extension state, a compression oil chamber (5) with an open top end is provided between every two adjacent piston rods (23) and between the piston rod (23) located at the outermost layer and the hydraulic cylinder body (1). A guide sleeve (6) is provided at the open end of each compression oil chamber (5). Each guide sleeve (6) is connected to the piston rod (23) located outside the compression oil chamber (5). The guide sleeve (6) located at the outermost layer is connected to the hydraulic cylinder body (1). When any of the piston rods (23) reaches the maximum extension state, a retraction start groove (7) connected to the oil return port (231) on the piston rod (23) is provided between the piston (22) connected to the piston rod (23) and the guide sleeve (6) abutting against the piston (22).

3. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 2 is characterized in that: The retraction start groove (7) comprises at least one of a first groove (71) provided at the end of the piston (22) and a second groove (72) provided at the bottom of the guide sleeve (6).

4. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 2 is characterized in that: The flow rate of the second chamber oil port (32) is the same as the total flow rate of all the oil return ports (231) on each of the piston rods (23).

5. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 2 is characterized in that: The cross-sectional area of ​​the compression oil chamber (5) decreases from the inner layer to the outer layer.

6. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1, characterized in that: The axial area of ​​the extension start groove (221) on each of the piston assemblies (2) decreases from the outside to the inside.

7. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1, characterized in that: The bottom of each piston assembly (2) has a plurality of oil holes (222) which are axially arranged and equidistantly distributed around the circumference, and the oil holes (222) located on different piston assemblies (2) do not intersect in the axial direction.

8. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1, characterized in that: Each guide sleeve (6) is connected to the piston rod (23) located outside the compression oil chamber (5) by means of a gland-type thread, and the guide sleeve (6) located at the outermost layer is connected to the hydraulic cylinder body (1) by means of a gland-type thread.

9. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1, characterized in that: The connecting accessory (3) is an earring, and the earring is threadedly connected to the top of the innermost piston assembly (2).

10. The multi-stage sequential telescopic hydraulic cylinder with step-by-step thrust change according to claim 1, characterized in that: The piston assembly (2) has five pistons.

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